Wave guide impedance transformer



April 6, 1948- w. w. HANSEN 2,438,914

WAVE GUIDE IMPEDANCE TRANSFORMER Filed June 19, 1945 2/ IIIIIIIIIH v 2 INVENTOR W/LL/AM m/m/mw ATTORNEY Patente d Apr. 6, 1948 2,438,914 GUIDE IMPEDANCE TRANSFORMER William W. Hansen, Garden City, N. Y., asslgnor to The Sperry Corporation, a corporation of Delaware Application June 19, 1943, Serial No. 491,429

Claims. 1

The present invention relates to the art including impedance matching and transforming devices especially adapted for use in systems utilizing high frequency electromagnetic energy conducted in wave guides.

In transferring energy from one high frequency device to another, it is well known that the impedances .thereof must be properly matched in order to avoid the production of standing Waves, with their attendant increase in losses and decrease in the energy transmitting capacity of the system. In addition, for greater efficiency of power transfer, it is known that the impedance of a load device must be properly matched to that of the high frequency source.

The present invention is directed toward the provision of improved impedance transforming devices which are adapted to transform an impedance connected at oneend to a different value at the other end of such a transforming device, whereby this transformed impedance may be matched to a. load or other impedance connected at such other end.

. Accordingly, it is an object of the present invention to provide improved impedance transformers for transforming a given impedance into a desired impedance.

Another object of the present invention is to provide an improved adjustable impedance transformer for use in the system having a maximum ease of adjustment and range of impedance transformation.

It is still ianother object of the present invention to provide an improved impedance transformer which is relatively insensitive to the changes in operating frequency.

Still another object of the present invention is to provide improved wave guide impedance transformers which are substantially independent of frequency over a considerable range of operation.

Other objects and advantages will become apparent from the following specification and drawings, in which Fig. 1 shows a longitudinal cross-sectional view of one form of adjustable wave guide impedance transformer.

Fig. 2 shows a corresponding longitudinal cross-sectional view of another form of adjustable wave guide impedance transformer having enlarged range of operation.

The present invention is useful especially in the connection between a high frequency source and a radiating wave guide. Such radiating wave guides in general require impedance matching devices to match them to the wave guides through which the input energy flows. Such devices form the present invention.

Fig. 1 shows a rectangular radiating wave guide 2 I incross-section, whose radiating slot begins at the point I9 and which is attached to a main or illustrated and described in connection with a nadiating wave guide, this specific application is merely one manner wherein these transformers may be employed. Hence, this illustrative eXam- Dle should not be taken in a limiting or restrictive sense. It will be apparent from the following description that such transformers may be used with diverse kinds of utilization apparatus, generally characterized by the fact that the apparatus connected to one end of the transformer is of a complex impedance which is different from that of the apparatus connected to the other end.

An adjustable wave guide transformer is shown in Fig. 1, generally designated by the numeral 22, and comprising a pair of shunt or tap wave guides 4| and 42 communicating with the main wave guide 2|. Each of these wave guides 41, 42 carries a sliding short-circuiting plunger 43 and 44, respectively slidable therein by manipulation of their adjustment knobs 4B and 41. Such a pair of adjustable shunt wave guides provides means for matching or transforming impediances over a substantial range, by suitably adjusting knobs 46 and 41 as required.

It has been found that when the distance d separating these shunt wave guides is substantially one-quarter-wavelength of the operating frequency, least sensitivity of adjustment is encountered; that is, adjustment of the knobs 4S and 41 produces relatively small change in impedance transformation, so that the device is relatively easy to adjust to a desired condition. However, for this quarter-wave relation, it has also been found that the range of impedance transformations attainable is somewhat restricted, so that not all impedance transformation values can be obtained.

By reducing the distance d, it is found that the range of permissible transformations increases, but, at the same time, the criticalness of adjustment of sliding pistons or plungers 43 and 44 increases, so that for too small a separation d the device becomes difficult to adjust accurately and to maintain in adjustment. A suitable compromise value has been found to be one-eighth of a wavelength, which is therefore the desired relation.

I have found that a wave guide impedance transformer which may be used to transform any arbitrary impedance connected at one end to any other arbitraryimpedance may be constructed by providing a triple shunt wave guide arrangement instead of the double shunt wave guide arrange- 3 tion of one more adjustable wave guide in shunt with the principal guide and appropriately spaced from the"pair;.of. guides 4l,= 42,: the range of impedances which can be transformedbr'match'ed is considerably extended.

of said further sections, and means for adjusting two of said shorting means independently of .one1 anotherrtoiitransformian. impedance at one endof" said principal section to a desired value at Fig. 2 shows such an improved form of transformer similar to the device of- Fig; lg'bllb in which thnee shunt wave guides are used, namely, 5|, 52 and 53, each having its respectiveshort circuiting piston 54, 55 and 56. Inpracticethe'condition of impedance match or proper impedance transformation is most often tested joy. observing the standing wave ratio or the pow-er output. Thus, in the device of Fig. 1, it will be clear that adjustments of the two plungers 43, 44 must be made by trial and error toproduce the zdesired'z result. Usually this willbe accomplished by setting toneof 1 the plungers, say plungersA3,'to'aniintermediate optimum position; which generally,will' not beithe desired condition, and then" resetting the;- other: r plunger to improve thiswio ptimum condition.

Then, by: alternately resetting each-of 3the-two plungers, the proper transforming condition may be bbtained after a few manipulations.

However, when three.adjustableplungers arepresented for setting, as in the devic opFigi 2, the problem of finding the proper adjustment is greatly-complicatedby the introduction of zone additional' degree of freedom. To. compensate :for this inherent complication,- pistons 54 'and tt are;;

joined by a yoke 51 andarejoint1y operable'by --knob--58. Piston-55 is= operablelbyfthe knobw59.

It will be noted that the yoke 51 is off-set to permit the two knobs 58 and 59 to pass one another.

Then, inoperationfthe three-plunger device ismanipulated in substantially the same manner as the 'two-plunger transformer requiringonly theindependent adjustmentoftwo plungenknobs I thereby producing variations of threeshunt wave guides. In-this manner; I have widened the 'op- 'erable-range of the Wave guide impedance transformer without sacrificing the ease and simplicity of adjustment.

Preferably, the respective pistons =are-separated by one-quarter of a Wavelength,- and under these circumstances it has been found that the device will satisfactorily transform impedancesoverithe "entire range of desired transformations. 'L'Fur- 'thermore; the sensitivity ofa'djustmentis such as to permit accurate and easy determination of the proper setting for the desired impedance transformationfThus the deviceof'Figl 2 is-to be preferred to'that of Fig. 1.

While the'devicesof Figs. 1 and 2 have beendescribed with nespect ftc' rectangularwave guides;

it is to be'noted that they "can "operate-just as satisfactorilyand inexactlythe same manner with wave guides of other'shapes, such-as circular; e1- liptical, etc.

As many changes could be madein the above" construction and manyapparently widelydiff-erent embodiments'oi this invention'could-be'made without departing "from "the scopethereof, it is intended that all mattei-"contained-in thealbove respectively spaced apart a distance. substantially equal to -one-quarter wavelengthat the-operating the other end of said principal section.

2. An adjustable wave guide impedance trans- Iormeri-comprisi n a first section of wave guide,

a. plurality of shunt single-conductor hollow-pipe wave guide sections at least three in number comm ur'i'ciating withisaid first section, adjustable shorting means'for each of said shunt sections,

:- ameansiiomsimultaneously adjusting at least two of said shunt-section-shorting means, and means forindependently adjusting another of said shunt-section-shorting. means, whereby an imrpedance connectedat one .end .of said'firstrsection 1 maybe transformed-to a desired .v'aluerat the "other :end ofisaid firstasection.

l 3.-'An :adjustablezimpedanceztransformen:apparatus for wave guides comprising-' a'firstisection of wave; guideuthneeshunt:single 'oonductor hol- .-sa id-:.:first'section;: and tcorrsecutively spaced ."alonglow-.piperwave guideesections communicating with V saidifirstu-section, adjus-table shortinga means for "each of \zs'aidishunt .sections;;.means for; adjusting itheshortingmeansaofithe center one of said shunt sect-ions; andsmeansaior .simultaneouslyvadjuse ing ithe-tsh'ortingz meansni the .:.outer ones of :said three sections-;=independent1y ofqisaid center-section-shorting means;wherebyanimpedance conmIIeC'bed" at one;:end of zsaid'f-first section may be transformed to axlesired value'atsthemther'end 10f isaidlfirsh secti'on by simultaneous adjustment of i aid ut r-Lsections; andtiseparatesadjustment= of ntheether oft-said 'shuntsections.

4.; An adjustable wavezguide :impedancetransiiormerfor transforming anarbitrary impedance to any other desired impedance zcomprising a principal wave guidersec-tion, aeplura'lityof furthen singleeconductor: hollowe'pipe waveaguide sections at leastthreeTinanumber: in .shunt with said principal section, ansiadjustable:shorting means; for :each of .tsaidf' further sections, and -=means for conjointlyi'ad'justingztwo of said shorting: means independently Pci'theiremainderof said plurality of shorting means.

5. An adjustable impedance transformen'appa- :ratus' ion wave guides comprising a firstasection "ofwave guideg': three =shunt wave guide sections communicatingwith: said fi rst section and consecutively spaced therealong-substantially a'quarter wavelengthapartatthe operating f-requency of said" apparatus, adjustable shorting "means for -aeachotisaid shunt sections; and means for simul- :taneously :adjusting t'the outer .rones 0f qsai-di three sections, whereby an impedance connected atone end of saidfirst section maybe transfo-rmedto a,

" desired value at: the tithe-rend of said first section by simultaneous adjustment of said 'outersections :andi separate: adjustment 50f the: .other. of said "shuntesections.

Number frequency," an adjustable'shorting 'means for each WILLIAM SEN.

:1 REFERENCES CITED 1 The following references "are of record in- -the file of this patent:

a, UNI-TED STATES PATENTS 'Name 1 Date -Ki-ng .5 Aug: 3, .1937 Southworth fi Feb. 1, '1938 Southworth Feb. I, 1938 2,155,508 Schelkunoff Apr. ::25', 1939 223231 79 King Feb; 18,1941 1 25284529 -Ii -Mason -May--26, 1 942 apes-n49 2,106,768 2,106,769 

